This invention relates to a drive mechanism for a plane reading device.
In a plane reading device for a copying machine or the like, an original is placed on the platen, which is fixed, and then a reading mechanism set above or below the platen is moved parallel to the platen, to read the image data of the original. One example of the drive device of a reading mechanism of a conventional plate reading device is as shown in FIG. 1. The reading mechanism 2 is arranged below a platen 1 in such a manner as to be movable along a guide rail 3 in parallel with the platen 1. When a stepping motor 4 is driven, drive force is transmitted through a transmitting member 5 comprising a wire or belt to a driving pulley 6, so that the reading mechanism 2 is moved in parallel with the platen 1 by a transmitting member 8 which is laid over the driving pulley 6 and a driven pulley 7.
In the conventional drive device, the transmitting member 5 and 8 are made of a flexible wire or belt. Therefore, the drive device is disadvantageous in that, when the reading mechanism 2 is moved stepwise, the transmitting members 5 and 8 are expanded slightly, as a result of which, when the stepping motor 4 has stopped, the reading mechanism 2 is vibrated, thus degrading the quality of the read image. In order to overcome this difficulty, a plane reading device has been proposed in the art, in which cylindrical frictional members 9 of felt or the like are interposed between the reading mechanism 2 and the guide rail 3, to damp the vibration of the reading mechanism 2. However, the plane reading device is still disadvantageous in that the frictional member 9 obstructs the movement of the reading mechanism; i.e., it is difficult to smoothly move the reading mechanism 2 because of the frictional member 9. As a result, the time required for movement in each stepping operation becomes longer, and accordingly it becomes difficult to read image data at high speed.